As liquid polymer materials, silicone, polyalkylene glycol, polyvinyl ether and the like are known, and they are used in heating media, lubricants, oils and the like. In these applications, the liquid polymer is preferably water-soluble if maintenance such as cleaning is taken into consideration.
Silicon is a polymer material having excellent lubricity, but it is very poor in affinity to water and thus lacking in water-solubility, and therefore its applications are limited.
Furthermore, polyethylene glycol, which is a typical example of polyalkylene glycol, is liquid by itself in the region having a low molecular weight to a middle molecular weight and excellent in water-solubility, but does not have a sufficient heat resistance. That of a high molecular range, the other hand, becomes crystalline, not liquid, and is so difficult to handle.
Furthermore, polyvinyl methyl ether, which is a typical example of polyvinyl ether, has compatibility with warm water, but is far from water-soluble.
Consequently, it is no exaggeration to state that almost no polymer material that can be provided for various purposes as a polymer material, which is liquid itself, has excellent water-solubility, and has also heat resistance and the like, is known, and it is earnestly desired to develop such a polymer material by the market.
On the other hand, as an art related to the present invention, a copolymer prepared by copolymerizing trioxane and 1,3-dioxolane is known in a considerably wide range. For example, a copolymer prepared by copolymerizing trioxane as a main component and a small amount of 1,3-dioxolane is known as a polyacetal copolymer, which is formed into machine parts and the like and widely used as an excellent thermo-plastic resin material having a high melting point, but it goes without saying that such a polyacetal copolymer does not show such a property as the (co)polymer of the present invention.
A copolymer prepared by copolymerizing trioxane and a large amount of 1.3-dioxolane is disclosed in each of JP-B 42-22065, U.S. Pat. No. 3,337,507, U.S. Pat. No. 4,788,258, equivalent to JP-A 1-131235), and U.S. Pat. No. 4,954,400, equivalent to JP-A 2-166184. However, the inventions disclosed in these Official Gazettes do not conceive of obtaining a liquid copolymer composed of trioxane and 1,3-dioxolane. For example, when the inventors of the present invention performed further testing of the copolymer composed of trioxane and 64 mol % of 1,3-dioxolane which is exemplified in JP-B 42-22065, such a copolymer was solid at room temperature and the copolymer described in U.S. Pat. No. 3,337,507 is also solid at room temperature from the description of the embodiment. The copolymer described in U.S. Pat. No. 4,788,258, equivalent to JP-A 1-131235, is also an amorphous copolymer having a low glass transition temperature, but it is not considered to be a liquid polymer in view of a copolymerization amount of 1,3-dioxolane. Furthermore, the copolymer disclosed in U.S. Pat. No. 4,954,400, equivalent to JP-A 2-166184, is a rubbery copolymer prepared by copolymerizing a small amount of a bi-functional monomer in addition to trioxane and 1,3-dioxolane, and is not a liquid polymer as in the present invention. In addition, these copolymers are rapid in depolymerization and therefore they have insufficient thermal stability.